A typical wireless communication system includes a number of base stations each radiating to provide coverage in which to serve user equipment devices (UEs) such as cell phones, tablet computers, tracking devices, embedded wireless modules, and other wirelessly equipped devices, whether or not user operated. In turn, each base station may connect with a core network that includes entities such as a network controller and a gateway system that provides connectivity with an external transport network such as the Internet. With this arrangement, a UE within coverage of the system may engage in air interface communication with a base station and may thereby communicate via the base station with various remote network entities or with other UEs served by the base station.
Such a system could operate in accordance with a particular radio access protocol, examples of which include, without limitation, Long Term Evolution (LTE) (using Orthogonal Frequency Division Multiple Access (OFDMA) and Single Carrier Frequency Division Multiple Access (SC-FDMA), Code Division Multiple Access (CDMA) (e.g., 1×RTT and 1×EV-DO), Global System for Mobile Communications (GSM), IEEE 802.11 (WIFI), BLUETOOTH, and others. Each protocol may define its own procedures for registration of UEs, initiation of communications, handover between base station coverage areas, and other functions.
Each base station coverage area in such a system could define an air interface on one or more carriers (carrier frequencies), providing uplink and downlink frequency bandwidth multiplexed to establish air interface resources for carrying communications between the base station and UEs. For instance, in LTE, the air interface could span a frequency bandwidth such as 10 MHz, 15 MHz, or 20 MHz, and the air interface is divided over frequency into 15 kHz subcarriers, and over time into 10-millisecond frames each divided into ten 1-millisecond subframes, in turn divided into 14 symbol time segments. With this arrangement, the LTE air interface defines an array of resource elements each occupying a 15 kHz subcarrier and a single symbol time segment, and each resource element can be modulated to carry data.
When a UE initially enters into coverage of such a system and detects coverage on a carrier, the UE could engage in a process to establish a radio-link layer connection with a base station that provides the coverage and could then engage in an attach process through which the system becomes configured to serve the UE. In an example attach process, the UE transmits an attach request over the air to the base station, and the base station forwards the attach request to the network controller in the core network. After authenticating and authorizing the UE, the network controller then engages in signaling with the base station and with the gateway system, to coordinate and trigger establishment of one or more network connections for the UE. In particular, this process results in setup of one or more bearer connections or “bearers” each defining a communication channel extending between the UE and the gateway system via the base station, including a radio portion extending between the UE and the base station and an access portion extending between the base station and the gateway system. Further, the gateway system or an associated server could assign an Internet Protocol (IP) address for use by the UE to engage in packet data communication.
Any such bearer established for a UE may have a corresponding defined service level, which could be indicated by one or more bearer attributes stored in context records for the UE at entities along the bearer path, such as at the UE, the base station, and the gateway system. For example, the service level could be indicated by a quality of service class identifier (QCI) and/or corresponding differentiated services point code (DSCP) value, which could be predefined to require handling of communications along the bearer in a particular manner. For instance, a high QCI level bearer, such as a bearer with any of QCIs 1-5, could have a designated guaranteed minimum bit rate (GBR), so entities along the bearer path would treat communications on the bearer as having relatively high priority as compared with other communications, in an effort to satisfy that minimum bit-rate requirement. Whereas a low QCI level bearer, such as a bearer with any of QCIs 6-9, could be deemed to receive merely best-efforts service, with no guaranteed minimum bit rate.
In a representative system, when a UE first attaches, the network could establish for the UE a default QCI 9 (best efforts) bearer for carrying general Internet communications such as e-mail, web browsing, and file transfer communications. Further, if the UE supports voice over Internet Protocol (VoIP) service, the network could also initially establish for the UE a QCI 5 bearer for carrying VoIP call control signaling (e.g., Session Initiation Protocol (SIP) signaling), so that the UE can engage in signaling to set up VoIP calls. Further, when a UE places or receives a VoIP call, the network could then further establish for the UE a QCI 1 bearer for carrying conversational-voice traffic (digitized, encoded voice data) of the VoIP call. Other bearers could also be established for the UE as appropriate.
Each such bearer could support communication between the UE and the gateway system and thus ultimately between the UE and a packet data network with which the gateway system provides connectivity. For instance, when data arrives at the gateway system for transmission along a particular bearer to the UE, the gateway system could transmit the data to the base station, the base station could allocate downlink air interface resources to carry the data to the UE, and the base station could then transmit the data on those allocated resources to the UE. And when the UE has data to transmit along a particular bearer to the gateway system for transmission on the packet data network, the base station could allocate uplink air interface resources to carry the data from the UE, the UE could transmit the data on those allocated resources to the base station, and the base station then transmit the data to the gateway system for output onto the packet data network.
To help ensure that sufficient air interface resources are available to be allocated for use to serve a GBR bearer, a GBR bearer could also have a designated maximum bit rate, indicating the highest bit rate that the bearer would be expected to support. The maximum bit rate could be based on the type of communication that the bearer is expected to carry. For instance, a QCI 1 bearer established for carrying voice traffic could have a designated maximum bit rate based on the bit rate of a voice codec that is or would likely be used for a voice call, such as 50 kilobits-per-second for example. Whereas, a QCI 2 bearer designated to carry live video streaming could have a designated maximum bit rate based on the bit rate of a video codec that is or would likely be used for the video stream, which might range from a few hundred kilobits per second to tens of megabits per second.
When the network controller sets up such a GBR bearer (e.g., when the UE engages in session initiation signaling such as SIP signaling to set up the associated communication), the network controller could inform the base station what the bearer's designated maximum bit rate is, and the base station could store that designated maximum bit rate in the UE's context record as an attribute of the bearer. Pursuant to the designated maximum bit rate, the base station could then reserve for the bearer a certain extent of air interface resources that would be sufficient to accommodate that maximum bit rate. For instance, the base station could determine, based on air interface channel quality reported by the UE, what quantity of air interface resources (e.g., resource elements) per unit time would be needed in order to carry data communication with the UE at the maximum bit rate, and the base station could reserve that quantity of air interface resource elements per unit time, to help ensure that the air interface can accommodate communication with the UE at up to that bit rate on the GBR bearer.